This invention relates to a relay apparatus for relaying a to-be-treated object between a transfer arm for transferring the object to and from a treatment chamber, and a cassette for storing the object.
In a semiconductor manufacturing process these days, a multi-chamber treatment apparatus, a so-called cluster tool, is used which is constituted of a common transfer chamber and various chambers (such as vacuum treatment chambers, a cassette chamber, etc.) situated around the common transfer chamber and connected thereto. At the time of using the cluster tool, a cassette which stores a plurality of to-be-treated objects is set in a cassette chamber, and one or more of the objects stored in the cassette set in the cassette chamber are transferred therefrom to the common transfer chamber. Then, the objects are subjected to positional alignment performed by a pre-alignment unit located in the common transfer chamber, and transferred to a predetermined vacuum treatment chamber by the transfer arm. In the vacuum treatment chamber, the objects are subjected to an etching treatment, a sputtering treatment, a CVD treatment, etc. The thus treated objects are transferred out of the vacuum chamber by the transfer arm and returned, via the common transfer chamber, to the cassette in the cassette chamber.
In a case where the cassette is of a so-called open type, the cassette chamber is necessary to isolate the objects from the outside. However, in a case where the cassette is of a so-called sealed type, the cassette chamber is not always necessary since the cassette itself can isolate the objects. In the latter case, where the cassette chamber is not used, the sealed type cassette is connected, directly or via a relay chamber, to the common transfer chamber.
Where the sealed type cassette is connected to the common transfer chamber via the relay chamber, to-be-treated objects stored in the cassette are transferred to the relay chamber by transfer means. In the relay chamber, the objects are shifted from the transfer means to the transfer arm. Then, the objects are transferred to the common transfer chamber by the transfer arm. At the time of shifting the objects, in particular, simultaneously, from the transfer means to the transfer arm, the objects may well move from a predetermined position on the transfer means or arm, or fall therefrom because of the vibration of the transfer means or arm, or because of the vibration of a gate valve located between the relay chamber and the common transfer chambers, which will occur at the time of opening or closing the valve. Moreover, also when the transfer of the objects between the transfer means and the transfer arm is interrupted for some reason, they may well move or fall. In addition, if there is a pressure difference between the common transfer chamber and the relay chamber, a turbulence will occur when the gate valve provided between the common transfer chamber and the relay chamber for isolating them from each other is opened, which may cause the movement or fall of the objects.
Furthermore, at the time of transferring the objects between the cassette and the relay chamber or between the transfer means and the transfer arm, dust particles may rise and stick to the objects since the relay chamber is shifted between a vacuum pressure and the atmospheric pressure. The same can be said of the case where the objects are temporarily put in the relay chamber before they are transferred from the transfer means to the transfer arm. Therefore, while the objects are transferred, it is necessary to take measure so that no dust or impurity will stick to to-be-treated surfaces of the objects.